Liquid color closed loop refill method and apparatus

ABSTRACT

Method and apparatus for furnishing process machines with liquid color from a supply thereof provides a loop conduit having respective ends receiving liquid color from the supply and discharging liquid color back into the supply, pumping liquid color through the loop conduit and discharging liquid color from the loop conduit at an intermediate position into a reservoir associated with a process machine upon liquid color level in the reservoir being at a low level limit.

CROSS-REFERENCE TO RELATED PATENT APPLICATION

This patent application is a 35 USC 120 continuation application of U.S.Ser. No. 14/620,345, now published as United States patent publicationU.S. 2015-0233369 A1, filed 12 Feb. 2015 in the name of Stephen B.Maguire and entitled “Method and Apparatus for Closed Loop AutomaticRefill of Liquid Color,” which in turn claimed the benefit of thepriority of U.S. provisional application Ser. No. 61/939,816 filed 14Feb. 2014 in the name of Stephen B. Maguire and entitled “Liquid ColorClosed Loop Automatic Refill System”; the priority was claimed under 35USC 119 and 35 USC 120; such priority is also claimed for thisapplication.

STATEMENT REGARDING FEDERAL FINANCING RESPECTING THIS INVENTION

Not applicable.

BACKGROUND OF THE INVENTION

Liquid color is metered from containers. When the liquid runs out and aprocess machine, namely an injection molding machine or extruder, isoperating producing plastic parts, there is a time period where no coloris being metered, and production parts must be scrapped because they donot get the required color. One solution is to alarm when color level islow, and change the liquid color container before the liquid color runsout. However, this results in the remaining liquid color being wasted,or a mess due to spillage, when transferring the remaining liquid colorinto the new container.

A better solution is to simply refill the container before the liquidcolor runs out. Currently available systems for doing this involve alevel sensor to detect low level in the primary container, and then areserve container and pump standing by for refilling the primarycontainer.

The reserve container may be small, but preferably is large enough tolast for many weeks. Two thousand pound capacity totes are standard inthe industry.

This reserve container may be very close, or may be located at somedistance. In either case a pump is required for the reserve containerfor transferring the liquid color into the primary container.

Factories always have many process machines. Each requires its ownprimary supply of color, and its own metering pump. In current systemsif, for example, 5 process machines are running and automatic refill ofthese containers is desired, then each process machine requires its own“reserve” container and a reserve pump as well. This need for 5 reservecontainers and 5 pumps is still present even if all process machines arerunning the same color.

SUMMARY OF THE INVENTION

When multiple process machines are running the same color, a moreefficient system as provided by the instant invention is to have onelarge reserve container with a pump to resupply all primary containers.

That is how the system of this invention works. One large reservecontainer is preferably used to refill each of the primary containerswhen any one of the primary containers runs low on liquid color.

As a further refinement, this invention preferably also incorporates aclosed loop system to supply liquid color to all of the processmachines. Liquid is preferably continuously pumped out through a pipingsystem that reaches all of the process machines and then returns to thereserve container. This assures a constant supply of “fresh” liquidcolor, with no risk of the liquid color settling or separating in theliquid color supply lines. (Settling can occur when liquid color heavilyloaded with pigment is left sitting in the liquid color supply conduit.)As an added benefit, this continuous flow also assures continuousturnover of liquid color and mixing of the liquid color in the reservecontainer.

When a primary container requires liquid color, the invention preferablyuses a diverter valve to divert the liquid color flow from thecirculation loop into the selected primary container. As an additionalfeature, to allow refill to occur as rapidly as possible, the inventionpreferably increases the pump rate of the circulation pump to itsmaximum. When not refilling a container the recirculation pump rate isslowed to a rate that is reasonable and that conserves energy, or in themost preferred practice of the invention, conserves compressed air thatis preferably used to drive the pump.

As an added feature of the invention, metering systems, with one locatedat each process machine, use load cells to control meteringgravimetrically. The load cells are also available to signal the propertime for refill to occur. Level sensors can be used in place of the loadcells.

In one of its aspects, this invention provides a method for furnishingprocess machines with liquid color from a supply thereof where themethod preferably commences with providing a loop conduit havingrespective ends receiving liquid color from the supply and dischargingliquid color into the supply. The method preferably proceeds withpumping liquid color through the loop conduit. The method thendischarges liquid color from the loop conduit at an intermediateposition thereon into a reservoir associated with a process machine uponthe process machine signaling a need for liquid color.

The method may further include providing at least one valve in theconduit for discharging liquid color therefrom and discharging liquidcolor from the loop conduit by actuating the valve.

In another one of its aspects, this invention preferably providesapparatus for furnishing process machines with liquid color where theapparatus preferably includes a supply of liquid color, a loop conduitfor carrying liquid color with the loop conduit preferably running fromthe supply to the process machines and back to the supply, a pump forcirculating liquid color around the loop, a detector for sensing whenliquid color is needed by an associated process machine, and a valve inthe loop for diverting liquid color from the loop to the associatedprocess machine upon the detector sensing the need for replenishment. Inan apparatus aspect of the invention, a solenoid is preferably providedfor actuating the valve. Furthermore in an apparatus aspect of theinvention, segments of the loop conduit are preferably structurallymounted adjacent to one another such that liquid color travels inopposite directions in the mounted segments and the valve is in one ofthe segments.

In still another one of its aspects, this invention provides a methodfor furnishing process machines such as injection molding presses,compression molding presses and extruders, and ancillary machines suchas receivers and gravimetric blenders, with liquid color from a supplyof liquid color. In one of these method aspects, the invention proceedsby providing a loop conduit having respective ends receiving liquidcolor from the supply and discharging liquid color back into the supply,and discharging liquid color from the conduit loop at an intermediateposition thereon into a reservoir associated with a process machine uponthe process machine signaling a need for liquid color.

The method may further include intermittently mixing liquid color in thesupply or continuously mixing liquid color in the supply.

In yet another one of its aspects, the method may further includeincreasing pumping speed whenever liquid color is being discharged fromthe loop conduit into a reservoir associated with a process machine. Themethod may further include providing at least one diverter valve in theconduit for discharging liquid color from the conduit, and specificallydischarging the liquid color from the liquid conduit by actuating thediverter valve.

In still another aspect of the invention, the invention embraces thesteps of sensing weight of the reservoir and upon sensed weight of thereservoir falling below a pre-selected value, actuating a diverter valveto discharge liquid color from the conduit to replenish the reservoir.

The method may further embrace sensing the weight of the reservoir andupon sensed reservoir weight falling below a pre-selected value,discharging liquid color from the conduit to replenish the reservoir.

The method may further embrace the step of increasing pumping speed uponsensed reservoir weight decreasing to within a pre-selected amount ofthe pre-selected level and decreasing pumping speed upon sensedreservoir weight increasing to at least the pre-determined level.

In another one of its aspects, this invention provides a method forfurnishing process machines with liquid color from a supply by providinga loop conduit having respective ends receiving liquid color from thesupply and discharging liquid color into the supply, pumping liquidcolor through the loop conduit, mixing liquid color in the supply,providing at least one valve in the conduit for discharging liquid colortherefrom, discharging liquid color from the loop conduit into areservoir associated with the process machine by opening a valve in theloop conduit upon the process machine signaling a need for liquid color,halting discharge of liquid color from the loop conduit, and increasingpumping speed upon sensed reservoir weight decreasing to within apre-selected amount of the pre-selected level but decreasing pumpingspeed upon sensed reservoir weight increasing to at least thepre-determined level.

In still yet another one of its aspects, this invention providesapparatus for furnishing process machines with liquid color where theapparatus includes a loop conduit for carrying liquid color running fromthe supply to the process machines and back to the supply, a pump forcirculating liquid color around the loop, a detector for sensing whenadditional liquid color is needed by an associated process machine, anda valve in the loop for diverting liquid color from the loop to theassociated process machine upon the detector sensing the need forreplenishment. The apparatus may further include a reservoir associatedwith each process machine for temporarily storing liquid color receivedfrom the loop conduit until needed by the process machine and a loadcell for detecting the weight of the reservoir and hence the amount ofliquid color therein.

The apparatus may further preferably include a solenoid for actuatingthe valve.

In one more aspect of the apparatus, segments of the loop conduit may bestructurally mounted adjacent to one another such that liquid colortravels at opposite directions in the mounted segments and the valve isin one of those segments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of apparatus embodying the methodfor practicing aspects of the invention.

FIG. 2 is an artist's rendition, in isometric form, of apparatusmanifesting aspects of the invention and showing a number of processmachines receiving liquid color in accordance with the invention.

FIG. 3 is an isometric drawing of a portion of a loop conduit of theinvention, with a diverter valve positioned therein, with the conduitand the diverter valve mounted on a common support structure.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings in general and to FIG. 1 in particular,apparatus embodying the invention and suitable for practice the methodaspects of the invention is designated generally 10 and includes a loopconduit 12 leading from a liquid color supply 16 to a pump 14. From thepump 14, the loop conduit 12 proceeds to a diverter valve 18 and fromdiverter valve 18 on around to the liquid color supply 16 to depositliquid color that has not been diverted by valve 18 back into liquidcolor supply 16. Diverter valve 18, when actuated, diverts liquid colorfrom loop conduit 12 down through supply conduit 28 into a reservoir orholding tank 20.

A load cell 22 senses the weight of reservoir or holding tank 20 andthereby senses the weight of liquid color within reservoir or holdingtank 20. Load cell 22 may be supported by structure resting on a floor26. It is to be understood that any suitable structure may be used forsupporting load cell 22 in a position to sense the weight of reservoiror holding tank 20.

An agitator or mixer 24 is provided for mixing liquid color within asupply 16. Agitator or mixer 24 is depicted only schematically. Agitatoror mixer 24 is conventionally motor-driven.

Diverter valve 18 is preferably actuated by solenoid 30. Upon actuationof valve 18 by solenoid 30, liquid color flowing through loop conduit 12is diverted to flow down through supply conduit 28 into reservoir orholding tank 20, rather than flowing around the remainder of loopconduit 12 and back into liquid color supply 16.

Solenoid 30 actuates diverter valve 18 to open diverter valve 18 topermit flow of liquid color through supply conduit 28 into reservoir 20upon sensed weight of reservoir 20 being low, indicating a low level ofliquid color within reservoir 20. Weight sensing is performed by loadcell 22. Once load cell 22, which continuously senses weight ofreservoir or holding tank 20, senses that reservoir or holding tank 20is beginning to approach its maximum capacity for liquid color, a signalis sent to solenoid 30. The signal de-actuates diverter valve 18whereupon no liquid color is permitted to flow into supply conduit 28,but rather liquid color continues to flow through valve 18 around loopconduit 12 and back to liquid color supply 16.

The invention further embraces regulation of the speed of pump 14.Desirably the speed of pump 14 is increased upon the sensed weight ofreservoir 20 decreasing to within a pre-selected amount of apre-selected low level, but speed of pump 14 is decreased upon thesensed weight of reservoir 20 increasing to at least a pre-determinedhigh level.

The invention further embraces regulation of the mixing or agitationprovided by agitator/mixer 24 for liquid color in liquid color supply16. A feed line 38 leads from reservoir or holding tank 20 to theassociated process machine to supply liquid color to the processmachine, as indicated by the arrow in FIG. 1.

Referring now to FIG. 2 which is an artist's rendition of the manner inwhich the invention and apparatus embodying the invention might beinstalled in a plastic injection molding facility, apparatus inaccordance with the invention is designated generally 10 with the loopconduit designated generally 12 and a pump designated generally 14 beingassociated with a reservoir or holding tank 20, all as illustrated inFIG. 2. Valves 18 are provided for diverting liquid color from loopconduit 12 into individual reserve or holding tanks 20 with one suchreserve or holding tank 20 being associated with each one of the processmachines 34, which in the drawing are illustrated as injection moldingpresses. Valves 18 are not visible in FIG. 2.

Liquid color is delivered from individual reservoirs or holding tanks 20to the process machines 34 by feed line 38. There is one feed line 38for each reservoir/holding tank 20-process machine 34 combination asillustrated in FIG. 2. Weight of each reservoir or holding tank 20 ismeasured by an associated load cell 22 located preferably belowreservoir or holding tank 20. There is preferably an individual loadcell 22 for each reservoir or holding tank 20. Load cells 22 aresupported by suitable structure, which also supports the associatedreservoir or holding tank 20 and which preferably rests on a floor 26 ofthe facility in which process machines 34 are located.

An agitator or mixer is provided for liquid color residing in liquidcolor supply 16. Hoppers 36 associated with each one of process machines34, in this case injection molding presses, retain granular resin untilthe granular resin is needed by the molding machine for the manufactureof plastic parts.

Each reservoir/holding tank 20 is connected to loop conduit 12 by asupply conduit 28 leading downwardly from a diverter valve, not shown inFIG. 2, that when actuated by a solenoid, not shown in FIG. 2, divertsliquid color from loop conduit 12 downwardly through supply conduit 28into reservoir or holding tank 20.

A feed line 38 is provided for each of the reservoir/holdingtank-process machine combinations as illustrated in FIG. 2.

A controller 32 is provided for each reservoir or holding tank 20.Controller 32 actuates solenoid 30 thereby to open diverter valve 18 andpermit downward flow of liquid color, under pressure, from loop conduit12 into reservoir or holding tank 20.

FIG. 3 illustrates a mounting block/diverter valve/loop conduit segmentassembly, one of which is provided for each reserve holding tank 20.Mounting block 44 is mounted on a framework 46 that is associated withand supports reservoir/holding tank 20, load cell 22 and solenoid 30.Framework 46 is illustrated and designated so in FIG. 2, but is notillustrated in FIG. 3.

Mounting block 44 supports outbound segment 40 and inbound segment 42 ofloop conduit 12. A diverter valve 18 is provided in the outbound segmentof loop conduit 40 and is actuated by solenoid 30. Upon energizingsolenoid 30 and consequent activation of diverter valve 18, liquid colorflowing in the outbound segment 40 of loop conduit 12 is diverteddownwardly by valve 18 and flows through supply conduit 28 into aparticular reservoir or holding tank with which diverter valve 18 andsupply conduit 28 are associated. Arrows A and B in FIG. 3 denote thedirection of flow of liquid color with liquid color flowing outwardly asindicated by arrow A through outbound segment 40 of loop conduit 12 andliquid color returning to supply 16 through inbound segment 42 of loopconduit 12 as indicated by arrow B.

During operation, liquid color is desirably pumped continuously by pump14 out of liquid color supply 16 through loop conduit 12. With loopconduit 12 being a “continuous” conduit, loop conduit 12 reaches all ofprocess machines 34, albeit indirectly, through supply conduits 28 andfeed lines 38, with loop conduit 12 then returning to liquid colorsupply 16. This assures a constant supply of “fresh” liquid color withno risk of the liquid color settling or separating in the liquid colorsupply line, namely loop conduit 12. As an additional benefit, thiscontinuous flow through loop conduit 12 assures continuous turnover ofliquid color and mixing of the liquid color in liquid color supply 16.

When a reserve or holding tank 20 requires liquid color, diverter valve18 is actuated to divert liquid color from loop conduit 12, specificallyfrom the outbound segment 40 of loop conduit 12, into the associatedreservoir or holding tank 20. Preferably, when a reservoir or holdingtank 20 requires additional liquid color, the speed of pump 14 isincreased to drive liquid color through loop conduit 12 faster and athigher pressure, thereby to minimize the time required for liquid colorreplenishment into reservoir or holding tank 20. When not refilling areservoir or holding tank 20, pump 14 is preferably slowed to a ratethat is reasonable and conserves energy, while continuing to circulateliquid color around loop conduit 12.

The metering system, namely the solenoid 30 and controller 32 associatedwith each reservoir or holding tank 20 uses a load cell 22 to controlthe metering of liquid color into each reservoir or holding tank 20gravimetrically. Load cell 20 additionally signals the proper time forrefill to occur, namely when the amount of liquid color in reservoir orholding tank 20 is excessively low and there is risk that there will beinsufficient liquid color flowing through feed line 38 to satisfy theneeds of process machine 34. While use of load cells is preferable,level sensors in reserve or holding tank 20 may also be used in place ofload cells.

In another aspect of the invention, a detector may be providedassociated with a process machine 34 to indicate when liquid color isneeded by that associated process machine. The detector then providessignal to the controller 32 which actuates solenoid 30 to move divertervalve 18 so that liquid color is supplied through supply conduit 28 toreservoir/holding tank 20. Desirably, a signal is also provided at thattime to pump 14 to drive pump 14 at its maximum speed, to provide liquidcolor at high pressure thereby quickly filling the associated reserve orholding tank 20 and replenishing the liquid color needed by theassociated process machine 34.

As illustrated in FIG. 3, liquid color preferably moves in oppositedirections with respect to mounting block 44, thereby balancing anystresses on mounting block 44 resulting from the dynamic flow of liquidcolor in directions A and B in FIG. 3. Additionally, pumping speed ofpump 14 is desirably increased upon sensed weight of a reservoir orholding tank 20 decreasing to within a pre-selected amount of apre-selected level, while decreasing pumping speed upon the sensedreservoir weight increasing to at least the pre-determined level as aresult of the reservoir or holding tank 20 being filled with liquidcolor to a pre-determined level.

As discussed above and from the foregoing description of the exemplaryembodiments of the invention, it will be readily apparent to thoseskilled in the art to which the invention pertains that the principlesand particularly the structures disclosed herein and the methods of usethereof can be used for applications other than those specificallymentioned. All such applications of the invention are intended to becovered by the appended claims unless expressly excluded therefrom.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics of the invention. Thedisclosed embodiments are therefore to be considered in all respects asillustrative and not restrictive with the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription. All changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

As used in the claims herein, the term “comprising” means “including”while the term “consisting of” means “including so much and no more” andthe term “consisting essentially of” means including the recitedelements and those minor accessories required and known to be used inthe art to facilitate the invention as claimed. The scope of theinvention is, therefore, indicated by the appended claims rather than bythe foregoing description and all changes which come within the range ofequivalency of the claims are to be considered to be embraced within thescope of the claims.

I claim the following:
 1. A method for furnishing a plurality of processmachines with liquid color from a supply thereof, comprising: a.providing a loop conduit having outbound and inbound segments withrespective ends receiving liquid color from the supply and dischargingliquid color back into the supply; b. continuously pumping liquid colorthrough the loop conduit; c. providing a plurality of liquid colordischarge positions in the outbound segment; d. discharging liquid colorfrom the loop conduit at one of the liquid color discharge positions onthe outboard segment into a respective reservoir connected by a supplyconduit to a respective process machine upon liquid color level in therespective reservoir being at a gravimetrically determined low levellimit or upon a detector connected to the respective process machinesignaling the need for liquid color by the machine.
 2. The method ofclaim 1 further comprising intermittently mixing liquid color in thesupply.
 3. The method of claim 1 further comprising continuously mixingliquid color in the supply.
 4. The method of claim 1 further comprisingincreasing pumping speed whenever liquid color is being discharged fromthe loop conduit into the reservoir.
 5. The method of claim 1 furthercomprising discharging liquid color from the loop conduit by actuating avalve.
 6. The method of claim 5 further comprising sensing weight of thereservoir and upon sensed weight falling below a preselected value,actuating the valve to discharge liquid color from the conduit toreplenish the reservoir.
 7. The method of claim 1 further comprisingsensing weight of the reservoir and upon sensed weight falling below apreselected value discharging liquid color from the conduit to replenishthe reservoir.
 8. The method of claim 2 further comprising sensingweight of the reservoir and upon sensed weight falling below apreselected value discharging liquid color from the conduit to replenishthe reservoir.
 9. The method of claim 5 further comprising: a.continuously sensing weight of the reservoir; b. replenishing thereservoir with liquid color from the conduit when sensed reservoirweight falls below a preselected level; and c. halting replenishment ofthe reservoir with liquid color from the conduit when sensed reservoirweight reaches a predetermined level.
 10. The method of claim 6 furthercomprising: a. continuously sensing weight of the reservoir; b. openingthe valve to replenish the reservoir with liquid color from the conduitwhen sensed reservoir weight falls below a preselected level; and c.closing the valve to halt replenishment of the reservoir with liquidcolor from the conduit when sensed reservoir weight reaches apredetermined level.
 11. The method of claim 1 further comprising: a.continuously sensing weight of the reservoir; b. opening a valve toreplenish the reservoir with liquid color from the conduit when sensedreservoir weight falls below a preselected level; and c. closing thevalve to halt replenishment of the reservoir with liquid color from theconduit when sensed reservoir weight reaches a predetermined level. 12.The method of claim 7 further comprising increasing pumping speed uponsensed reservoir weight decreasing to within a preselected amount of thepreselected level and decreasing pumping speed upon sensed reservoirweight increasing to at least the predetermined level.
 13. The method ofclaim 6 further comprising increasing pumping speed upon sensedreservoir weight decreasing to within a preselected amount of thepreselected level and decreasing pumping speed upon sensed reservoirweight increasing to at least the predetermined level.
 14. A method forfurnishing process machines with liquid color from a supply thereof,comprising: a. providing a loop conduit having respective ends receivingliquid color from the supply and discharging liquid color back into thesupply; b. pumping liquid color through the loop conduit; c. mixingliquid color in the supply; d. discharging liquid color from the loopconduit into a reservoir associated with a process machine by opening atleast one valve in the loop conduit upon the process machine signaling aneed for liquid color; e. halting discharge of liquid color from theloop conduit; f. increasing pumping speed upon sensed reservoir weightdecreasing to within a preselected amount of the preselected level anddecreasing pumping speed upon sensed reservoir weight increasing to atleast the predetermined level.
 15. Apparatus for furnishing processmachines with liquid color from a supply thereof, comprising: a. a loopconduit for carrying liquid color from the supply to the processmachine(s) and back to the supply; b. a pump for circulating liquidcolor around the loop conduit; c. a detector for sensing when additionalliquid color is needed by an associated process machine; d. a valve inthe loop conduit for diverting liquid color from the loop to theassociated process machine upon the detector sensing the need forreplenishment.
 16. Apparatus of claim 15 further comprising: a. areservoir associated with each process machine for temporarily storingliquid color received from the loop conduit until needed by the processmachine; and b. wherein the detector comprises a load cell for detectingthe weight of the reservoir and hence the amount of liquid colortherein.
 17. Apparatus of claim 16 further comprising a solenoid foractuating the valve.
 18. Apparatus of claim 17 wherein segments of theloop conduit are structurally mounted adjacent to one another such thatliquid color travels in opposite directions in the mounted segments andthe valve is in one of the segments.
 19. A method for furnishing processmachines with liquid color from a supply thereof, comprising: a.providing a loop conduit having respective ends receiving liquid colorfrom a supply and discharging liquid color back into the supply; b.pumping liquid color through the loop conduit; c. discharging liquidcolor from the loop conduit at an intermediate position thereon to aprocess machine upon liquid color level for the process machine being ata low level limit.
 20. The method of claim 19 further comprisingincreasing pumping speed upon liquid color level for the process machinebeing at the low level limit.
 21. A method for furnishing a plurality ofprocess machines with liquid color from a supply thereof, consisting of:a. providing a loop conduit having outbound and inbound segments withrespective ends receiving liquid color from the supply and dischargingliquid color back into the supply; b. continuously pumping liquid colorthrough the loop conduit; c. providing a plurality of liquid colordischarge positions in the outbound segment; d. discharging liquid colorfrom the loop conduit at one of the liquid color discharge positions onthe outboard segment into a respective reservoir connected by a supplyconduit to a respective process machine upon liquid color level in therespective reservoir being at a gravimetrically determined low levellimit or upon a detector connected to the respective process machinesignaling the need for liquid color by the machine.
 22. Apparatus forfurnishing process machines with liquid color from a supply thereof,consisting of: a. a loop conduit for carrying liquid color from thesupply to the process machine(s) and back to the supply; b. a pump forcirculating liquid color around the loop conduit; c. a detector forsensing when additional liquid color is needed by an associated processmachine; d. a valve in the loop conduit for diverting liquid color fromthe loop to the associated process machine upon the detector sensing theneed for replenishment.
 23. A method for furnishing process machineswith liquid color from a supply thereof, consisting of: a. providing aloop conduit having respective ends receiving liquid color from a supplyand discharging liquid color back into the supply; b. pumping liquidcolor through the loop conduit; c. discharging liquid color from theloop conduit at an intermediate position thereon to a process machineupon liquid color level for the process machine being at a low levellimit.
 24. Apparatus for furnishing process machines with liquid colorfrom a supply thereof, consisting essentially of: a. a loop conduit forcarrying liquid color from the supply to the process machine(s) and backto the supply; b. a pump for circulating liquid color around the loopconduit; c. a detector for sensing when additional liquid color isneeded by an associated process machine; d. a valve in the loop conduitfor diverting liquid color from the loop to the associated processmachine upon the detector sensing the need for replenishment.
 25. Amethod for furnishing process machines with liquid color from a supplythereof, consisting essentially of: a. providing a loop conduit havingrespective ends receiving liquid color from a supply and dischargingliquid color back into the supply; b. pumping liquid color through theloop conduit; c. discharging liquid color from the loop conduit at anintermediate position thereon to a process machine upon liquid colorlevel for the process machine being at a low level limit.